Shortened fastener with locally controlled thread height

ABSTRACT

A male anti-cross threading fastener comprising: a substantially round shank having a lead end, a torque end, and a plurality of male threads around a circumference of the shank, the plurality of male threads comprising: a standard thread around at least a portion of the circumference of the shank and having a standard thread contour, wherein a width and a thread angle of the standard thread enables engagement with corresponding female threads, wherein the major diameter of the standard thread is between a lower major diameter limit and a higher major diameter limit; a transitional thread around at least a portion of the circumference of the shank and having a transitional thread contour with a width and a thread angle similar to the width and thread angle of the standard thread that enables engagement with corresponding female threads; an anti-cross thread around at least a portion of the circumference of the shank and having an anti-cross thread contour and an outside diameter configured to promote alignment of the male anti-cross thread fastener with a female fastener; and a lead thread around at least a portion of the circumference of the shank and having a lead thread contour, and wherein the transitional thread contour has a height that transitions from the lower major diameter limit of the standard thread to the outside diameter of the anti-cross thread.

TECHNICAL FIELD

The present disclosure relates in general to the field of threadedfasteners such as screws and bolts and, more particularly, a transitionthread at the lead end of the thread helix.

BACKGROUND

U.S. Pat. No. 5,836,731 discloses an anti-cross thread fastener,incorporated in its entirety herein. FIG. 1 shows a side view of a knownanti-cross thread fastener, wherein the thread helix is different frommost fastener threads in that the helix comprises four sequentialcontours, rather than a standard thread contour for the entire length ofthe helix. These four thread contours include (listed in order from thefastener head to the lead end): (i) a standard, ISO-type thread contour10 wraps around the shank of the fastener for the majority of helixturns, such number of turns determined as required to achieve a desiredfunctional thread length; (ii) a transition thread contour 20 isadjacent the standard thread contour; (iii) an anti-cross thread contour30 has a radial profile, as describe in U.S. Pat. No. 5,836,731, and alength of approximately one complete turn of the helix; and (iv) a leadthread contour 40 having a length from one eighth turn to several turnsof the helix and functions to lead the thread helix into its mating witha female thread. U.S. Pat. No. 9,644,664, incorporated herein in itsentirety, describes a contour for the lead thread 40 that lends improvedanti-false-thread performance to the fastener. U.S. Pat. No. 6,561,741,incorporated herein in its entirety, describes a contour for the leadthread 40 that lends improved lead in performance to align the fastener.The lead thread contour 40 may also have other less ideal profiles.Anti-cross thread and anti-false-thread fasteners are commonly soldunder the tradenames MAThread® and MATpoint®.

The transitional thread contour 20 has two primary functions: (i) toform a smoothly blended transition between the standard ISO-type threadcontour 10 and the anti-cross thread contour 30; and (ii) to notinterfere with or create undue contact with the female thread duringthreading. Both of these functions are non-structural and do not requirea full height, standard thread.

To perform the first function, the transitional thread contour 20 hasone end that smoothly blends with the standard ISO-type thread contour10 and the other end that smoothly blends with the radial profile of theanti-cross thread contour 30. The height of the anti-cross threadcontour 30 is approximately half the height of the standard ISO-typethread contour 10. The transitional thread contour 20 must provide asmooth transition between these thread heights.

To perform the second function, the transitional thread contour 20decreases in height over its length. FIG. 2 shows a cross-sectional viewof two adjacent threads of a fastener taken along the longitudinalcentral axis of a fastener shank 14. The threads have standard parts.For example, the standard ISO-type thread contour 10 has troughs 11,flanks 12, and a crest 13, wherein the thread angle of the flanks 12 isapproximately sixty degrees. The flanks 12 are flat and extend from thetroughs 11 to the crest 13. The standard ISO-type thread contour 10 isthe tallest thread having a standard thread major diameter 16. Theanti-cross thread contour 30 is approximately half as tall having ananti-cross thread outside diameter 36, so that there is a difference inheight 62. The transitional thread contour 20 should transition, withoutinterfering with female threads of a female fastener as they engage withthe lead thread contour 40 and the anti-cross thread contour 30.

FIGS. 3A-3H provide a series of sequential cross-sectional views takenthrough the transition thread contour 20 as it wraps around the fastenershank 14. A straight line 61 extends across the tops of the transitionthread contour 20 in these figures to illustrate a constant reduction inthe height as the thread helix wraps around the shank 14. Thetransitional thread contour 20 is a blend or merge of the ISO-typestandard thread contour 10 (see FIG. 3A) and the anti-cross threadprofile 30 (see FIG. 3H). As a standard portion 21 of the transitionalthread contour 20 decreases in height, more and more of an anti-crossportion 22 protrudes to form the flanks 12 at the troughs 11. Thetransition thread contour 20 first appears as a slightly shorterstandard thread profile (see FIG. 3B), wherein the flanks 12 are at thesame angles and width of the crest 13 is the same as the standardISO-type standard thread contour 11. The difference being the profile isshifted down so the thread is shorter and the width between the troughs11 is narrower. In FIG. 3D, a standard portion 21 of the thread isshifted even further down so the transitional thread contour 20 is evenshorter. Also, with the standard portion 21 shifted down, an anti-crossportion 22 bulges to from the flanks adjacent the troughs 11. In FIG.3E, the standard portion 21 is shifted still further down so thetransitional thread contour 20 is even shorter and the anti-crossportion 22 forms even more of the flanks 12 adjacent the troughs 11. InFIG. 3F, the anti-cross portion 22 dominates with the standard portion21 forming a tip at the top of the transitional thread contour 20. InFIG. 3F, the transition thread contour 20 is similar to that shown inFIG. 3G, except the tip of the standard portion 21 protruding at the topof the anti-cross portion 22 is even shorter and narrower. Importantly,as shown in FIGS. 3B-3G, the crest 13 at the top of the standard portion21 maintains the same width, and the flanks 12 of the standard portion21 maintain the same flank angles.

FIGS. 4A-4H provide a series of sequential cross-sectional views takenthrough another known transitional thread contour 20 as it wraps arounda fastener shank 14. Rather than shifting the standard portion 21 down,this transitional thread contour 20 widens the flank angles of theflanks 12 of the standard portion 21. The transitional thread contour 20first appears as a slightly shorter standard thread profile (see FIG.4B), wherein width of the crest 13 is the same as the standard ISO-typestandard thread contour 11, but the flanks 12 are angled slightly widerso as to extend all the way to the troughs 11. In FIGS. 4C-4E, thetransitional thread contour 20 is shortened by maintaining the width ofthe crest 13 the same and angling the flanks 12 wider to extend to thetroughs 11. In FIG. 4F, the height of the transitional thread contour 20continues to be shortened so that the anti-cross portion 22 bulges toform the flanks at the troughs 11 and the flanks 12 of the standardportion 21 are widened to blend into the contour of the anti-crossportion 22. In FIG. 4G, the anti-cross portion 22 dominates with just asmall hump having a crest 13 at the top and very wide flanks 12 blendinginto the contour of the anti-cross portion 22.

The transitional thread contours 20 known to accomplish this transitionhave varied between the superimposed contours illustrated in FIGS. 3B-3Gand the more smoothly blended contours shown in FIGS. 4B-4G. Any shapebetween these contours is adequate to accomplish the transitionfunction.

The second function of the transitional thread contour, i.e., notinterfering with the female thread during use, may be satisfied with athread height that is never so high, anywhere along its length, that itmight interfere with, and/or jam, against the internal female thread ofa female fastener during the camming action of the male anti-crossthread fastener. A height decrease at an essentially linear rate as itprogresses around the helix from the full thread height to theanti-cross thread has been satisfactory. For example, an M8×1.25 6 gmetric transitional thread has been used with a constant heightreduction rate of approximately 0.0015 mm per degree of helix rotation.In FIGS. 3A-3H and 4A-4H, straight line 61 extends across the tops ofthe transition thread contour 20 to illustrate a constant reduction inthe height as the thread helix wraps around the shank 14. Transitionthread contours 20 having lengths from one-quarter turn (90 degrees) toone and one-quarter turns (450 degrees) have been utilized.

SUMMARY

Therefore a need exists for improved anti-cross thread fastener.

According to aspects of the invention, there is provided a maleanti-cross threading fastener comprising: a substantially round shankhaving a lead end, a torque end, and a plurality of male threads arounda circumference of the shank, the plurality of male threads comprising:a standard thread around at least a portion of the circumference of theshank and having a standard thread contour, wherein a width and a threadangle of the standard thread enables engagement with correspondingfemale threads, wherein the major diameter of the standard thread isbetween a lower major diameter limit and a higher major diameter limit;a transitional thread around at least a portion of the circumference ofthe shank and having a transitional thread contour with a width and athread angle similar to the width and thread angle of the standardthread that enables engagement with corresponding female threads; ananti-cross thread around at least a portion of the circumference of theshank and having an anti-cross thread contour and an outside diameterconfigured to promote alignment of the male anti-cross thread fastenerwith a female fastener; and a lead thread around at least a portion ofthe circumference of the shank and having a lead thread contour, andwherein the transitional thread contour has a height that transitionsfrom the lower major diameter limit of the standard thread to theoutside diameter of the anti-cross thread.

Another aspect of the invention provides a male anti-cross threadingfastener comprising: a substantially round shank having a lead end, atorque end, and a plurality of male threads around a circumference ofthe shank, the plurality of male threads comprising: a standard threadaround at least a portion of the circumference of the shank and having astandard thread contour defined by troughs, a flat crest, and flatflanks from the troughs to the crest and a thread angle of about sixtydegrees, wherein the major diameter of the standard thread is between alower major diameter limit and a higher major diameter limit; atransitional thread forming a continuous helix with the standard threadaround at least a portion of the circumference of the shank andcomprising a transitional thread contour defined by troughs, a flatcrest, and flat flanks from the troughs to the crest and a thread angleof about sixty degrees; an anti-cross thread forming a continuous helixwith the transitional thread around at least a portion of thecircumference of the shank and having an anti-cross thread contour andan outside diameter configured to promote alignment of the maleanti-cross thread fastener with a female fastener; and a lead threadforming a continuous helix with the anti-cross thread around at least aportion of the circumference of the shank and having a lead threadcontour, wherein the crest of the transitional thread contour widens andthe height of the transitional thread contour shortens as thetransitional thread contour transitions from the standard thread contourto the anti-cross thread contour.

According to still another aspect of the invention, there is provided amale anti-cross threading fastener comprising: a substantially roundshank having a lead end, a torque end, and a plurality of male threadsaround a circumference of the shank, the plurality of male threadscomprising: a standard thread around at least a portion of thecircumference of the shank and having a standard thread contour definedby troughs at a minimum diameter, a flat crest at a major diameter, andflat flanks from the troughs to the crest having a width at a pitchdiameter and a thread angle of about sixty degrees, wherein the majordiameter of the standard thread is between a lower major diameter limitand a higher major diameter limit; a transitional thread forming acontinuous helix with the standard thread around at least a portion ofthe circumference of the shank and comprising a transitional threadcontour defined by troughs, a flat crest, and flat flanks from thetroughs to the crest and a thread angle of about sixty degrees and aheight no higher than the lower major diameter limit of the standardthread contour, wherein the wherein the transitional thread winds lessthan about five-eighths of a turn (225 degrees) around the shank; and ananti-cross thread forming a continuous helix with the transitionalthread around at least a portion of the circumference of the shank andhaving an anti-cross thread contour comprising an outside diameterapproximately the same as the pitch diameter of the standard thread, andwherein the anti-cross thread contour comprises a shape defined by acurve extending from a curve at a trough to about the outer diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure may be acquiredby referring to the following description taken in conjunction with theaccompanying drawings wherein:

FIG. 1 illustrates a side view of a male anti-cross thread fastenerknown in the prior art;

FIG. 2 illustrates a cross-sectional side view of a standard thread andan anti-cross thread of the male anti-cross thread fastener shown inFIG. 1;

FIGS. 3A-3H provide a series of sequential cross-sectional views takenthrough a transition thread contour as it wraps around the fastenershank from the standard thread to the anti-cross thread;

FIGS. 4A-4H provide a series of sequential cross-sectional views takenthrough a transition thread contour as it wraps around the fastenershank from the standard thread to the anti-cross thread;

FIG. 5 illustrates a cross-sectional side view of a thread rolling dieand an anti-cross thread fastener being rolled in the die;

FIG. 6 shows a cross-sectional side view of a cutter tool for cuttingthread rolling groove in a thread rolling die;

FIG. 7A is a cross-sectional side view of an ISO-type standard threadcontour being rolled in a groove of a thread rolling die;

FIG. 7B is a cross-sectional side view of a transitional thread contourbeing rolled in a groove of a thread rolling die;

FIGS. 8A and 8B show end and side views, respectively, of a conventionalmale anti-cross thread fastener having a long transitional thread;

FIG. 9 illustrates a cross-sectional side view of a transitional threadcontour of the present invention;

FIG. 10 shows a cross-sectional side view of three threads of a fastenerbeing rolled in three adjacent grooves of a die to form a standardthread having a major diameter at a higher major diameter limit;

FIGS. 11A and 11B show end and side views of a male anti-cross threadfastener of the present invention;

FIGS. 12A and 12B show end and side views of a male anti-cross threadfastener of the present invention;

FIGS. 13A through 13D are cross-sectional side views of the transitionalthread taken at the sections indicated in FIG. 13E; and

FIG. 13E is an end view of male fastener cut-off at a transitionalthread contour.

While the present disclosure is susceptible to various modifications andalternative forms, specific example embodiments thereof have been shownin the drawings and are herein described in detail. It should beunderstood, however, that the description herein of specific exampleembodiments is not intended to limit the disclosure to the particularforms disclosed herein, but on the contrary, this disclosure is to coverall modifications and equivalents as defined by the appended claims.

DETAILED DESCRIPTION

According to the teachings of this disclosure, shorter fasteners arepossible while maintaining thread engagement and anti-cross threadfunctionality.

Aspects of the invention addresses what was previously a “fixed” lengthof the transitional thread contour of the thread helix on an anti-crossthreading fastener. Aspects of the invention include a method ofreducing the length of the transitional thread contour of the threadhelix on an anti-cross threading fastener, while maintaining fullanti-cross thread functionality.

The length of the transitional thread contour was previously considered“fixed” because the height transition can ideally be achieved in acalculated length of travel around the thread helix. In practice, thelength of the transitional thread contour is longer than the calculatedideal because it is not possible to achieve that ideal length usingtoday's production and manufacturing methods. This anomaly is due to twocurrent circumstances: 1) the use of a thread rolling die itself musthave its own build tolerances, and 2) the use of a process that mustallow for thread height tolerances.

Because of these limitations, the groove in the thread rolling die thatis actually utilized to form the transitional thread contour on thethread helix must be longer and deeper than that necessary to form ahelical ramp of the desired length on the fastener. This extra groovelength in the die requires extra “space” in the die, space that iswasted because it is not utilized to accomplish the necessary heightchange of the transitional thread contour that the die rolls duringthread-rolling. In essence the longer linear transition in the die thanactually desired, therefore, results in a longer helical transitionformed on the fastener helix.

The anti-cross thread fastener thread-rolling die may be formed byutilizing a standard thread-milling cutter and cutting a series oflinear grooves across the surface of the thread rolling die. When eachindividual cutter reaches a specified point, its cutting surface iswithdrawn from the workpiece (die) at a constant rate as the cuttercontinues to progress in a straight path across the die surface. Thegroove thusly cut on the die surface is linear, at a constant depth fora finite length, then angles up and out of the die. The angle thuslyformed at the bottom of the groove by the withdrawing cutter matches thegrowth rate desired for the transitional thread contour to be formed inthe fastener thread helix that the die will roll. The growth rate of thetransitional thread contour is shown as line 61 drawn across the tops ofthe thread sections illustrated in FIGS. 3A-3H and 4A-4H. The ideallinear angle at the bottom of the die groove produces a transitionalthread contour of about three-quarter turn (270 degrees) of the helix inlength when rolled on the fastener.

The angled portion of the grooves in the die that forms the transitionalthread contour must, in fact, be longer and deeper than the calculatedideal length of the transitional thread contour because of tolerances ofthe thread rolling die itself and the thread height tolerances. Withlonger and deeper grooves in the die, the grooves are not completelyfilled with metal when forming the thread peak at their deepest point,and the grooves are narrower than the standard full thread for theentire length of the ramp in the die. These factors contribute to atransitional thread contour that does not have thread flanks at the samewidth and fullness a flanks of a standard thread. In particular, for theentire length of the ramp in the groove of the die, the transitionalthread contour helix that is rolled on the fastener by that die contouris technically not able to engage the flanks of the standard femalethreads. Even though the desired height change may be accomplished inthe desired three-quarter turn (270 degrees) of the helix, thetransitional thread contour continues for some distance beyond thatlength as a full height thread, but with narrower flanks compared to afull standard thread. As such, since the primary purpose of thetransitionary thread is to achieve the transition from ISO-type standardthread height down to anti-cross thread height, the transitional threadcontour has some portion of its length that is not needed to achieve thechange in height.

Referring now to the drawings, the details of example embodiments areschematically illustrated. Like elements in the drawings will berepresented by like numbers.

FIG. 5 illustrates a cross-sectional side view of a thread rolling die60 and an anti-cross thread fastener 50. The cross-section is taken downthe center of a thread rolling groove 63 in the thread rolling die 60.To illustrate the match between the die 60 and the fastener thread helixit rolls, the anti-cross thread fastener 50 is shown with its threadhelix “straightened” such that both the linear die groove and normallycurved thread helix peak appear as a linear ramp, rather than a curvedhelix actually seen on the fastener rolled with that die. The threadrolling groove 63 has a constant depth section 64 and a ramp section 65.The thread rolling groove 63 transitions from the constant depth section64 to the ramp section 65 at transition point 66, and the ramp section65 terminates at terminal point (not shown) at its intersection with theanti-cross thread profile cut. The constant depth section 64 of thethread rolling groove 63 forms an ISO-type standard thread contour 10 inthe anti-cross threading fastener 50. The ramp section 65 of the threadrolling groove 63 forms a transitional thread contour 20 in theanti-cross threading fastener 50. The length of the ramp section 65extends well beyond the point where the fastener peak has achievedstandard thread max height 16. This wasted length 68 of the threadrolling groove 63 is “wasted” because it does not fill with metal duringrolling, leaving a gap 69. Therefore, the wasted length 68 accomplishesno purpose other than providing tolerance space for over-full threads toform.

FIG. 6 shows a cross-sectional side view of a cutter tool 70 for cuttingthread rolling groove 63 in a die 60. In order for the cutter tool 70 tobe used to cut the constant depth section 64 in the thread rollinggroove 63 of the die 60 as shown in FIG. 5, it must have a longer point71 compared to a cutter designed to cut a nominally shaped thread, whichwould have a shorter point 72. Further, when cutting tool 70 isprogressively inserted to cut the ramp section 65, cutter tool 70 is toothin to cut a groove 63 in the die 60 wide enough to form a full-widthISO-type standard thread contour 10 until its cut reaches the maximumdepth in the die when it cuts the constant depth section 64. As such,the entire ramp section 65 of the groove 63 is cut with a cutter 71 thatis too narrow to form a full-width ISO-type standard thread contour 10.

FIG. 7A is a cross-sectional side view of an ISO-type standard threadcontour 10 being rolled by a die 60. FIG. 7B is a cross-sectional sideview of a transitional thread contour 20 being rolled by a die 60. Forillustration, a standard thread profile 17 is superimposed on the die inFIG. 7B. Comparatively, the standard portion 21 of the transitionalthread contour 20 formed in the transition area of the die 60 isnarrower across the flanks than the standard thread profile 17. Ineffect, this means that a length of the die real estate reserved for thetransition thread to grow to its peak height has been wasted by rollinga discrete part of the transition thread whose peak height 16 wasactually within the allowable height range of the standard thread peak,but, because it is too narrow, does not function as full thread. Thereis, therefore, a length of the thread helix, rolled by the transitionsection of the die 60, between the actual ramp of the transitionalthread contour and the point where the thread achieves full height andwidth that is there only because of the prior art means of manufacture.That transitionary die groove length is not necessary for transitionalthread ramp-up, as the thread peak achieves the necessary height to meeta minimum height requirement of the standard thread in the first part ofthe groove, the last section of the transitionary groove forms only atransitional thread contour that is above the minimum necessary heightand too narrow to be considered a full thread.

FIGS. 8A and 8B show end and side views, respectively, of a conventionalmale anti-cross thread fastener 50 having a long transitional threadcontour 20. The ISO-type standard thread contour 10 of the helix is fullwidth and height to a first change point 23 where the transitionalthread contour 20 begins. The transitional thread contour 20 of thehelix has a first section 24, between the first change point 23 and asecond change point 25, where the profile of the thread has a heightabove the minimum required for a full standard thread but a width toonarrow to function as a full standard thread. At second change point 25the height of the transitional thread contour 20 is reduced to the meanstandard thread height. In a second section 26 the helix profile isreduced in height, reaching the minimum standard thread height at point27, but is still too narrow to function as a full standard thread. Fromthe third change point 27, the transitional thread contour 20 begins toget shorter in height. Throughout a third section 28, the height andwidth of the transitional thread contour 20 is constantly reduced untilit reaches forth change point 29. The fourth change point 29 marks theend of the transitional thread contour 20 and the beginning of theanti-cross thread contour 30. Notably, the anti-cross portion 22 of theanti-cross thread contour 30 demonstrates the transitional threadcontour 20 is too thin to perform the function of a full standard threadover its entire length, including the first section 24. Prior to thepresent invention, anti-cross thread fasteners have had a transitionalthread contour 20 of this length and have included a “too-narrow” firstsection 24 of the helix.

According to some embodiments of the invention, this “too-narrow” lengthof transitional thread contour 20 may be eliminated to produce a shorteranti-cross thread fastener. To provide the shortest possiblefull-functioning anti-cross thread fastener, i.e., the least costly,shortest, lightest, and most package-able, this “too-narrow” length oftransitional thread contour 20 may be eliminated. Design of ananti-cross thread fastener according to the present invention may bepredicated on providing a method, of limiting the transition threadlength actually necessary to achieve the ramp-up to the minimumacceptable peak height, without the useless “too-narrow” section. Someembodiments of the invention include a novel contour for use on part ofthe helix of anti-cross thread fasteners that allows reducing the lengthof the transition thread, without negatively affecting thread functions.

Some embodiments of the invention provide a novel transition threadcontour for an anti-cross threading fasteners, thus allowing extra,non-functional, helix length to be eliminated from that section of thethread helix. Such improvement may be gained by reconfiguring the firstand second sections 24 and 26 of the transitional thread contour 20 ofthe helix shown in FIGS. 8A and 8B.

These two sections of transitionary helix are herein reconfigured byreforming each length of helix into a full standard-width threadcontour. The full-width helix sections are to be provided with a novel,variable, yet more closely controlled, peak height. In particular, apeak height totally within the range of acceptable peak-height values ofthe standard thread. According to aspects of the invention, thepeak-height values are deliberately reduced in a controlled manner, overthe combined helix length of the two sections first and second sections24 and 26, to the minimum acceptable standard thread profile height, atthe second change point 25 where second section 26 blends into thebeginning of the new, shorter transition thread.

By reconfiguring these sections of the helix, the thread effectivelybecome a “standard thread” such that the combined length of the firstand second sections 24 and 26 may be added to the existing standardthread helix, resulting in a longer standard-contour structural threadhelix, with a shorter section of helix reserved for only transitionaryfunction. This effectively allows a shorter fastener to accomplish thesame function.

According to aspects of the invention utilized on the anti-cross threadfastened described herein may result in a transition thread lengthapproximately one-quarter turns (90 degrees) shorter than a prior idealthread, while maintaining the function(s) of the prior transitionthread's rate of descent. Even tiny reductions in a fastener'snon-structural helix length may provide large advantages in function ofthe fastener. Therefore, various aspects of the invention may provide ashorter, lighter, less-costly, more package able fastener, with improvedanti-cross thread functionality.

Referring to FIG. 9, a cross-sectional side view of a transitionalthread contour 120 of the present invention is shown. The transitionalthread contour 120 has a thread height 118 significantly shorter thanthe possible height of the standard thread major diameter 116. Thestandard thread major diameter 116 may be formed by completely fillingthe die in a mean position adequate to meet standard threadrequirements. A transitional thread contour 120 having a relativelyshorter thread height 118 maintains all the characteristics of thestandard thread except for the height. Because the thread height 118 ofthe transitional thread contour 120 is more closely controlled, thethread does not need to be maintained within the same significanttolerance range, and may be shorter to bring the localized peak heightdown to a more valuable height, while maintaining its full width andflank angles to provide fastening characteristics. This relativelyshorter thread height 118 may allow the transitional thread contour 120of the helix to start at a lower height.

This very localized deliberate reduction in thread peak height, assumingit is only localized, with the remainder of the standard thread helixremaining at full height and full tolerance, still gives themanufacturer freedom to vary the standard thread peak height on all butthis repurposed section of the transitionary thread, as may be requiredby that manufacturer's processes and/or customer requirements.

According to aspects of the invention, standard-type, anti-cross threadrolling dies may be provided with a reduced-depth section in the diegroove that always preferentially fills completely. FIG. 10 is across-sectional side view of three threads of a fastener 150 beingrolled in three adjacent grooves of a die 160 for forming a standardthread having a major diameter at a higher major diameter limit 115. Inthe first groove, the thread material of the fastener is pressed into ashorter, more restrictive groove to completely fill the groove to athread profile having a more restricted, having a height at a lowermajor diameter limit 116. In the second groove, the thread material ofthe fastener is pressed into a full depth groove to partially fill thegroove to a mean major diameter limit 114. In the third groove, thethread material of the fastener is pressed into a full depth groove tofill the groove to a higher major diameter limit 115 having a maximumallowable height. During the thread rolling process, the metal flow isrestricted in a discrete section of the helix allowing the remainingfull thread helix length to under-fill to varying degrees within itsallowable height range, i.e., between the lower major diameter limit 116and the higher major diameter limit 115, to meet the individualmanufacturer's requirements for the full thread height of a standardthread having a major diameter, without in any way affecting the rollingprocess or function of the structural threads. Such preferential fillingof the lower profile repurposed section may occur even when the adjacentfull standard thread helix is manufactured with its peak at the lowermajor diameter limit 116.

Aspects of the invention provide a deliberate localized reduction inthread height in the area adjacent the transition thread may shorten the‘ramp’ necessary to reach the peak of the anti-cross thread fastener toprovide an effectively shorter transition thread and enabling reducedlength anti-cross thread fasteners. A portion of the thread helix on amale anti-cross threading fastener of the type discussed above may becontoured to shorten the effective length of the anti-cross threadfastener's helix. The transition section of the helix, may not exceedone turn (360 degrees) of the thread helix in length, may begin at theend of the standard turns of the fastener helix at the point on thestandard turns most distal from the fastener's head, and may end at theanti-cross thread.

A transitional thread contour according to aspects of the invention maybe contoured so that its tallest point is blended with the full-heightstandard threads of the helix. From there, the transitional threadcontour section of the helix may be reduced in height at a specifiedrate as it winds around the fastener shank to its shortest point. Atransitional thread contour starts at the point where the nominal fullheight major diameter of the standard thread helix first decreases inheight and blends through approximately one-quarter turn (90 degrees) ofthe helix to continue to reduce the height of the thread whilemaintaining flanks similar to a standard thread. During the reduction inpeak-height, the transitional thread contour maintains a flank width andthread angle consistent with a standard thread profile, yet always be ofa height approximately equal to the minimum acceptable for a fullstandard thread defined as the lower major diameter limit 116.

The full standard thread section of the helix may thereby gain a similarlength of functionally equivalent thread and the transitional section ofthe helix may thereby be reduced in length by an equivalent amount. Themale anti-cross threading fastener may have appropriate anticrossthreading features adjacent the leading end of the transition thread aswell as an appropriate lead thread, and appropriate piloting features onthe point of the fastener. An example of an appropriate piloting featureon the point of the fastener is the lead-in point 5 at the lead end ofthe shank 14, shown in FIG. 1. It is anticipated that this constructionmight also be utilized on other types of fasteners, as well asanti-cross threading fasteners that have a shorter, i.e., less ideallength transition thread, to improve their function.

Referring to FIGS. 11A and 11B, end and side views of a male anti-crossthread fastener of the present invention are shown. An ISO-type standardthread contour 110 of the helix has a full standard thread width andheight to a first change point 123. At the first change point 123 thehelix thread has a mean standard thread height and full standard threadflank width and thread angle of sixty degrees. (See 115 in FIG. 10).This flank width and peak height is maintained for the entire firstsection 124 to second change point 125. Over the second section 126 fromthe second change point 125 to a third change point 127, the helixprofile is constantly reduced in height 118 at the preferred rate, tothe mean major diameter limit 114 for standard-thread height (minimumacceptable) (see 114 in FIG. 10) at the third change point 127.Throughout the second section 126 the flank width of the flanks ismaintained as that the standard fastener profile. As shown in FIG. 11B,the crest of the thread throughout the second section 126 grows widerfrom the second change point 125 to the third change point 127. Alsoshown in FIG. 11B, the flat flanks of the thread throughout the secondsection 126 are maintained at the troughs from the second change point125 to the third change point 127.

With further reference to FIGS. 11A and 11B, a third section 128 extendsfrom third change point 127 to the fourth change point 129. At the thirdchange point 127, the thread contour is that of a standard thread 110having been reduced to its minimum height and maintained standard flankwidth. The transitional thread contour 120 begins with this profile atthe third change point 127 and transitions until it assumes theanti-cross thread profile at the fourth change point 129. The transitionthread contour 120 may begin at the third change point 127 and ends atthe fourth change point 129, such that it winds around the shank 14 forabout five-eighths of a turn (225 degrees).

FIGS. 12A and 12B show end and side views of a male anti-cross threadfastener. In this embodiment, the fastener threads have a maximummaterial condition, meaning that the thread peaks are at their highestrelative to the pitch line and the groove in the die that forms suchpeak would be completely full of material. A notable difference betweenthis embodiment and the one illustrated in FIGS. 11A and 11B is that thefull thread height is at a restricted, lower maximum permissible height(see 116 in FIG. 10) at the first change point 123 in the helix thread,rather than a higher standard thread height. (See 115 in FIG. 10). In arestricted, maximum material condition, the peak would be expected toflow to the maximum allowable height within the threading die groove.The thread peak is instead deliberately controlled to be shorter thanthe expected flow height, with this controlled height falling at theconstant preferred rate to the mean height peak, while maintaining thefull flank width. This difference in thread tolerance and manufactureresults in constant growth of the transition helix section throughoutthe third section 128, rather than the constant height through the firstsection 124 (see FIG. 11A). This variation in height demonstrates the“free-flow” of metal to this height in a fastener utilizing the extrememajor diameter.

As can be seen in comparing the drawings (FIGS. 11A-11B, and 12A-12B)the length of an effective full standard thread is increased byreconfiguring the first section 124 and a second section 126 to befull-width threads, while the overall length of the fastener helix ismaintained.

FIG. 13E is an end view of male fastener cut-off at a transitionalthread contour and FIGS. 13A through 13D are cross-sectional side viewsof the transitional thread taken at the sections indicated in FIG. 13E.The transitional thread contour 120 has a width as wide as the profileof the standard thread, while gradually reducing the height of the peakfrom the maximum allowable to the minimum allowable for a standardthread. As shown in FIGS. 13A-13D, the width of the transitional threadcontour 120 remains constant and is as wide as the profile of thestandard thread. As shown in FIG. 13D, the transitional thread contour120 is at its height 118 as tall as the higher major diameter limit 115.See 115 in FIG. 10. As shown in FIG. 13C, the transitional threadcontour 120 is shorter having a height 118 not quite as tall as themaximum allowable for the standard thread 115. As shown in FIG. 13B, thetransitional thread contour 120 is shorter still having a height 118 notquite as short as the mean major diameter limit 114 for the standardthread. See 114 in FIG. 10. As shown in FIG. 13A, the transitionalthread contour 120 has a height 118 approximately equal to the minimumacceptable for a full standard thread defined as the lower majordiameter limit 116. See 116 in FIG. 10.

Because the transitional thread contour 120 has flanks the same width asthe standard thread, the length of the ISO-type standard thread portionof the helix may be shortened. In particular, it may be shortened by thelength of the transitional thread contour 120 from the first changepoint 123 to the third change point 127. This portion of thetransitional thread contour 120 replaces a previously functionallyunneeded section, allowing it to now be considered a standard thread,adding usable length to the standard thread helix. As such, theadditional full thread may be utilized in fastened joint design, or,alternatively, the overall length, of the fastener may be reduced byshortening the standard thread by the amount of added low-profilestandard thread, thus reducing weight, and cost.

The transitional thread contour 120 of the present invention may bemanufactured as part of the thread helix of a male anti-cross threadfastener by deliberately providing a reduced diameter section of thefastener blank to the rolling die, causing a particular localizedsection of the thread rolling die to under-fill with metal duringrolling, in order to allow free-flow of metal to achieve the desiredshape. Alternatively, the transitional thread contour 120 may bemachined to a lower height in some localize area of the helix. Eithermethod may create a full-width, reduced-height section of the helix.

While embodiments of this disclosure have been depicted, described, andare defined by reference to example embodiments of the disclosure, suchreferences do not imply a limitation on the disclosure, and no suchlimitation is to be inferred. The subject matter disclosed is capable ofconsiderable modification, alteration, and equivalents in form andfunction, as will occur to those ordinarily skilled in the pertinent artand having the benefit of this disclosure. The depicted and describedembodiments of this disclosure are examples only, and are not exhaustiveof the scope of the disclosure.

What is claimed is:
 1. A male anti-cross threading fastener comprising:a substantially round shank having a lead end, a torque end, and aplurality of male threads around a circumference of the shank, theplurality of male threads comprising: a standard thread around at leasta portion of the circumference of the shank and having a standard threadcontour defined by troughs, a flat crest, and flat flanks from thetroughs to the crest and a thread angle of about sixty degrees, whereinthe major diameter of the standard thread is between a lower majordiameter limit and a higher major diameter limit; a transitional threadforming a continuous helix with the standard thread around at least aportion of the circumference of the shank and comprising a transitionalthread contour defined by troughs, a flat crest, and flat flanks fromthe troughs to the crest and a thread angle of about sixty degrees; ananti-cross thread forming a continuous helix with the transitionalthread around at least a portion of the circumference of the shank andhaving an anti-cross thread contour and an outside diameter configuredto promote alignment of the male anti-cross thread fastener with afemale fastener; and a lead thread forming a continuous helix with theanti-cross thread around at least a portion of the circumference of theshank and having a lead thread contour, wherein the crest of thetransitional thread contour widens and the height of the transitionalthread contour shortens as the transitional thread contour transitionsfrom the standard thread contour to the anti-cross thread contour,wherein the outside diameter of the anti-cross thread is approximatelythe same as a pitch diameter of the standard thread, and wherein theanti-cross thread contour comprises a shape defined by a curve extendingfrom a curve at the trough to about the outer diameter.
 2. Theanti-cross threading fastener of claim 1, wherein the transitionalthread winds less than about five-eighths of a turn (225 degrees) aroundthe shank.
 3. The anti-cross threading fastener of claim 1, wherein thestandard thread, the transition thread, the anti-cross thread, and thelead thread comprise a continuous thread helix around the shank.
 4. Theanti-cross threading fastener of claim 1, further comprising a lead-inpoint at the lead end of the shank.
 5. The anti-cross threading fastenerof claim 4, wherein the lead-in point comprises a variable outerdiameter and a length, wherein the variable outer diameter is maximumproximate to the lead end of the shank and becomes smaller toward an endof the lead-in point distal from the lead end of the shank.